@conference {69514,
	title = {Genetic analysis of incidence of clinical mastitis in New Zealand dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {70},
	year = {2010},
	month = {Jun},
	pages = {246-249},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {The aim of the study was to estimate breed and geneticeffects on the incidence of clinical mastitis (CM) in New Zealand dairy cattle. Records of CM collected during seasons 2005-06 to 2008-09 from 53,419 cows of different breeds including Holstein-Friesian (H-F), Jersey (J) and Crossbed (HF x J), were analysed. Clinical mastitis was coded {\textquotedblleft}1{\textquotedblright} for cows that presented at least one event of CM at any day at risk during the season and {\textquotedblleft}0{\textquotedblright} for cows without CM. Genetic parameters and breed effects for the incidence of CM were estimated with a repeatability animal model across breeds using restricted maximum likelihood methodology. The cumulative lactation incidence of CM was 11\% in92,961 lactations. Heritability and repeatability for incidence of CM were 0.015 {\textpm} 0.003 and 0.070 {\textpm} 0.005, respectively. Jersey cowshad 2.9\% less incidence of CM than H-F cows. Heterosis effect of H-F x J was minus 11.7\% of the average of the parental breeds. Results from this study confirm previous estimates ofgenetic parameters for CM. Sire variation and breed and heterosis effects were significant and can be exploited in a breeding program to improve resistance to CM in New Zealand dairy cattle.},
	issn = {1176-5283},
	author = {Jury K and Lopez-Villalobos N and Spelman RJ and Arias J and Heuer C}
}
@conference {41887,
	title = {Bovine viral diarrhoea virus in dairy cattle in New Zealand - studies on its prevalence, biologic and economic impact},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {162-167},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {The majority (>90\%) of dairy cattle will conceive following insemination or natural service, but only about 55\% of cattle calve to any single mating. The majority of losses occur before the time of pregnancy recognition and such cattle are generally detected in oestrus and rebred. However, losses do occur after the period of pregnancy recognition resulting in prolonged duration of open periods and increased probability of culling for infertility. Reasons for loss include genetic abnormalities, infectious agents such as Neospora caninum, bovine viral diarrhoea virus (BVDV), and plant toxicities. The incidence, causes and economic impact of pregnancy loss are poorly defined in New Zealand. In a survey of bulk tank milk, 93\% of 141 dairy herds had >10\% of cows with BVDV antibody. In another study, 602 herds with a high vs. low bulk tank milk (BTM) BVDV antibody concentration were associated with 1.7\% higher annual abortion rates, 2.9d longer calving to conception intervals, 0.04 more services/conception, and 1kg/d reduced solid corrected milk production. Losses due to BVDV were assessed as $90/cow/year in affected herds. It is concluded that pregnancy loss imposes significant economic costs on the New Zealand dairy industry and that BVDV is likely to be major contributing causative agent. Further research is required to evaluate the effects of BVDV on reproduction in dairy herds, the risk factors for the disease and the cost:benefit of control or eradication strategies. },
	issn = {1176-5283},
	author = {Compton CWR and McDougall S and Heuer C}
}
@conference {41372,
	title = {Computer simulation of Johne{\textquoteright}s disease in New Zealand cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {62},
	year = {2002},
	month = {Jan},
	pages = {294-298},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {<p>Control options for Johne\&rsquo;s disease (JD) are explored by computer simulation because intervention trials under field conditions would be too costly. The purpose of this review is to describe a simulation model developed in The Netherlands and adapted to dairy herds in Pennsylvania (USA). The paper consequently derives what information is required for the adaptation to New Zealand dairy herds and explains the methods by which that information is currently collected. The model \&lsquo;JohneSSim\&rsquo; simulates the within herd development of JD based on time related changes. Time intervals are six months. JD is transmitted vertically through the placenta or from dam to calf around calving through direct contact, colostrum, rest milk or bulk milk, infected pasture, or through contact with adult replacement stock from other herds. Control options include test-and-cull, measures to prevent the infection of calves, vaccination, and grouping of animals by age. The simulation suggested that, in The Netherlands as well as in Pennsylvania, progressively improving calf-hygiene with little reliance on test-and-culling would decrease the prevalence considerably and was economically feasible (average benefit-costs-ratio excluding extra labor = 1.58). Test-and-cull was not economical even if a test with 80\% sensitivity was available. Contract heifer rearing, colostrum management, and seasonal calving appear to be risk factors for transmission that have specific relevance for New Zealand dairy herds.</p>},
	issn = {1176-5283},
	author = {Soons R and Heuer C and Jackson R and Groenedaal H}
}
